2015 VW Golf TDI = 65 mpg!

The advantage of diesel is much smaller (or non-existent) when you compare it even to a modern gasoline engine (Skyactiv, TSI ...)

For example new 1.4 TSI with ACT gets 33.6 MPG (7 l/100 km), a 2.0 TDI gets 38.7 MPG (6.07 l/100 km). Both cars have similar performance, the petrol has a little less power but it's lighter:
Übersicht: Volkswagen - Golf - Spritmonitor.de

Similar picture if you compare 1.2 TSI with 1.6 TDI, both have 105 HP, a little more torque from the diesel is offset by a lighter petrol car. Result 37.2 MPG (6.32 l/100 km) vs 42 MPG (5.58 l/100 km):
Übersicht: Volkswagen - Golf - Spritmonitor.de

And the Mazda example:
Übersicht: Mazda - CX-5 - Spritmonitor.de
Übersicht: Mazda - 6 - Spritmonitor.de

And one more correction of your statement, 30% more efficiency is not the same as 30% more MPG. Efficiency is measured from the energy input and energy output. And funny part is that energy content difference is roughly the same as CO2 difference per volume of fuel (13 %). Therefore CO2 emission is a very accurate measure of cars efficiency.

Making an engine efficient costs additional money, ask you self where do efficient diesel cars come from? Europe. Ask your self why there wasn't an efficient petrol engine till now? Because the diesel was cheaper in many European country's, the petrol engine was always in a much cheaper car and it had to be simple. Things are changing now with the demand for CO2 reduction and diesel getting on the petrol price level.

And one more note, it's no coincidence that the most efficient petrol car (Prius) was born in Japan. Diesel was just not an option there because of emissions.

And why there is no efficient car from US? Well take a look at the petrol prices and correct me if I'm wrong no additional taxes on bigger engines or CO2 emissions.

 

The TSI is also has .6 fewer liters of displacement. I'm not sure how much difference it makes, but I think the most apples-to-apples comparison is the 6-speed 2.0 TDI vs the 6-speed 2.0 gasoline Jetta.
(But you are right that it takes extra $$ to make the 1.4 gasoline engines that good, so they are doing what hybrids are doing.....making a gasoline engine more efficient by adding cost and technology, as opposed to just making a diesel version)

If costs is our concern (probably #1 priority for most ppl), we can compare the two.
As I mentioned above, DD = 1.14 based on current price difference between diesel and gasoline.

So, 38.7 mpg on the 2.0 diesel translates to 33.95 mpge..........barely better than 1.4 TSI's 33.6 mpg.....pretty much a tie

The 1.6 TDI gets 42 mpg..........which becomes 36.84 mpge, slightly less than 1.2 TSI's 37.2 mpg.......again, a virtual tie

Yes, you're right but I think the misunderstanding is in whether we are talking about the 'efficiency' of the fuel or the efficiency of the engine. Of course, diesel cars get better mpg because of both.

I use 'efficiency' in quotes, because fuel is not traditionally measured in this term. So, what I mean is the volumetric energy density of diesel fuel, or, to put it more precisely:

How many BTU's can be packed into the space of 1 gallon of a particular fuel?

From Wikipedia:
Gasoline gallon equivalent - Wikipedia, the free encyclopedia

We see that regular Diesel #2 contains 129,500 BTUs per gallon
And summer gasoline (no E10) contains 114,500 BTUs (winter has 112,500 BTUs) so I'll use 113,500 BTU/gal

Well, 129,500 is 14% more BTUs than 113,500. This corresponds with what you were saying, which is that the higher energy content is due to the higher carbon content (and thus higher co2 emissions)

This makes sense. The energy of a fossil fuel is stored in the Carbon-Hydrogen bonds, and 1 gallon of diesel will contain more of these than 1 gallon of gasoline. More carbon = more energy

BTU's is the ultimate expression of work, and we know that diesel has 14% more BTU's than gasoline per unit volume.

But we also know that diesel cars always get far more than 14% more miles gallon compared to gasoline versions of the same car.........usually they can go 30% further.

This is where engine efficiency comes in. The diesel compression are just inherently more efficient than spark-engine, again with ALL THINGS BEING EQUAL.

Obviously, adding more technology or hybridizing the drivetrain will improve both, but diesel will retain its ability to deliver more mpg all the way up the efficiency ladder to a ranger extender for a PHEV.

The natural efficiency advantage of a diesel is probably on the order of 15-16% or so........when added to the 13-14% more energy in a gallon of diesel fuel, you end up with 30% more miles per gallon.

30% more miles to the gallon sounds great as a diesel marketing term.........it really makes that engine look good!

What they don't tell you is that the diesel tech is only part of the reason, with the choice of fuel being the other, unsung hero here.

Diesel technology is only superior to the extent that it can improve mileage above and beyond what one would already expect when starting with the highest energy density fossil fuel there is!!

 

Ok
I think I was reading too much into the negative connotations of the terms deflator and disadvantage, and seeing the comparison mpg as the the diesel number being knocked down.

On the issue of price, the majority see the price per gallon for premium gas and diesel being higher, and automatically discount such vehicles without taking into account the fact those vehicles go farther on a gallon of fuel. GM has to say the 1.4L in the Sonic and Cruze is a regular fuel engine, because being honest and saying premium would hurt sales. But, from experimentation, the Sonic will get 2mpg more, and be cheaper per mile with a 25 cent price difference.

Using the DD to calculate mpge could lead to errors. I didn't check it, but do know adjusting a diesel mpg by the percent difference in energy content between gas and diesel can give slightly different results than by actually calculating the mpge. MPG is a poor metric that should be converted to gal/mi or such before performing calculations.

Did you see the disconnect?
We shouldn't buy diesels because money spent on diesels is money not spent pushing hybrid and EV tech and acceptance. We also shouldn't buy diesels because there isn't the large scale investment for biodiesel, but there is for EV infrastructure.

Diesel, improved gasoline, CNG, EV, and their hybrid derivatives will all have a part to play. I see EV as the goal, but their limitations mean the ICE still has a future. Bio-diesel appears to be a better avenue than ethanol. Unfortunately, most of the available car models were made for perto-diesel only.

As for foreign oil dependence, diesel doesn't seem to be a big contributor. It appears that the over seas demand for it just makes it too valuable to convert into gasoline to use here. The Jetta and Passat TDI sell at about the same numbers as the Camry hybrid and Prius C. Increasing the selection of diesel models is only going to have zero to a positive impact on our foreign oil dependence.

 

Ummm.........I'm pretty sure the mpg claims of the diesel-hybrid Range Rover are spot-on.

No, I don't think Range Rover engineers will be winning a Nobel Prize.........

They didn't break the laws of physics, they just added a plug:

LAND ROVER REVEALS ITS FIRST FULLY CAPABLE 4WD PLUG-IN DIESEL HYBRID | Land Rover International

20 mile AER, should return lower co2 g/mile than Prius if plugged in every 40-50 miles or so (I'm assuming 0g carbon for the grid electricity, but of course my main concern would be getting off foreign oil, so I'd be happy with 100% W. Virginia coal instead of 20% OPEC oil )

 

This is the best comparison of hybrid versus diesel I have read.
2013 VW Jetta Comparison Test: Hybrid vs. TDI vs. GLI vs. 2.5 – Review – Car and Driver

Let's change things around, we should realize YMMV. They are a good choice for those that don't want hybrids, or in very high highway mixes, or in cars where diesel and not hybrid are available.

One problem with the vw tdi is they will not accept a high percentage of biodiesel.

It should be low dependance on foreign oil with more diesel used. The crack advantage is small though, because US refineries can export the diesel and petroleum coke. Ghg production from oil refining would be reduced if the coke was not exported (this is the fuel grade, high in sulfur, normally burned like high sulfur coal), but it offsets coal in the countries that import it. Large exports of coke go to latin america and China.

 

Yeah, the VW's only except 5% biodiesel, and that may also be true of the BMWs and Mercedes. The Cruze, along with the GM and Ford trucks, can take up to 20%.

 

Yes I see the disconnect, but IMHO Bio-Diesel had their chance.
They obviously weren't ready to take on Petro-Diesel priced at $4, so now LNG is stepping in to take their place in this 'fight'.

IIRC the infrastructure costs and technical hurdles for installing public L2 (and even L3) EV charging stations is minor compared to this (and other plans to mass-produce algae oil):
Fed Awards $100 Million to Sapphire for Algae - TENTHMIL

That is not to say they can't be overcome.

I am very much rooting for algae biodiesel to succeed, because we are going to need every weapon in our arsenal if we truly understand the scale of this problem and the scope of the challenge.

Btw, it looks like both Solazyme and Sapphire received federal monies.
So, one couldn't reasonably say that EVs are only succeeding now because they've received more government money than advanced biofuels. They have simply overcome technical hurdles faster, as we've seen w./ Tesla.

So it appears that for now, the race for alternate energy is shaping up like this (in terms of which technology reduces foreign oil usage most per dollar spent):

1st Place: EV's and PHEV's
2nd Place: Petro-Diesel and crop-based Biodiesels
3rd Place: crop-based Ethanol
4th Place: Algae Biodiesel & Cellulosic ethanol

I don't see algae fuels cracking the top 3 any time soon. In fact, they better check their rear-view mirrors, because Fuel Cells, Methanol, LNG and CNG are all coming up fast.

 

LNG is a 20 year bridge type of solution, its not a long term solution. I support the picken's plan.

Problem is politics. Koch brothers don't want to see natural gas used in trucking as it will raise the price, and they use lots of natural gas. Companies like toyota want to push hydrogen which requires cheap natural gas, and lng kills most of the reason to subsidize hydrogen. Nobody in washington seems to want higher oil taxes, but the easiest way to make LNG for trucking a majority fuel is to make diesel more expensive, otherwise you need subsidies or mandates to build the stations.

biodiesel is a longer term solution. Eventually oil and natural gas will run into shorter supplies while biodiesel relies manly on solar electricity with a little natural gas and electricity thrown in. Economics will push it, unless we become a hydrogen transportation economy. The question really is when not if.

These are not competing. Tesla and nissan seem to be putting up L3 stations. The federal government has so far helped plug-ins more than algea. This is the way it should be, algea is at a much earlier stage of development. Think of it this way. Algea based biodiesel should cost about $10/gallon in 2017. Exxon said pricing likely won't be viable until 2035 for cars. But what if there is wars. Biofuels from algea can also be used to power jets. Its therefore a strategic interest, and much cheaper than say invading a mid eastern country to get jet fuel.

Look out until 2035. Will we have phevs with ices powered by biofuels, or with fuel cells powered by hydrogen or methanol.

I am very much rooting for algae biodiesel to succeed, because we are going to need every weapon in our arsenal if we truly understand the scale of this problem and the scope of the challenge.

They all have gotten federal money. The biggest thing tesla did was have the audacity to leverage all that japanese government money for lithium cells, and figure out how to put them together in a reliable exceptional platform. Tesla would still work without US government money, but likely it would have taken much longer to get to where they are. The volt and leaf though were only greenlighted because of the tesla roadster, and promises of government money.

In the US algae based biofuels definitely look more feasible than fuel cells. It simply doesn't reaquire a new fueling infrastructure. It only has one technical challenge, that the price of oil goes up.
U.S. Perfectly Placed For Algae-Based Biofuel Production

Fuel cells have 3 major challenges.
1) The price of hydrogen is higher than both gasoline and electricity, so the same as algea, but a little less of a challenge.
2) Price of the vehicle is higher than phevs the competing technology. This is because of both the fuel cells and the tanks
3) The lack of fueling infrastructure, which will not be built without large government payments as long as both cars and fuels are much more expensive than competitive technologies. (a small 15,000 station national roll out would cost approximately $30B, but projections are it will take at least until 2025 to get a million fuel cell cars on the road, that means $3K per car to build a nation wide fueling network).

 

Perhaps we'll get lucky and thermal depolymerization will gain traction.

Thermal depolymerization - Wikipedia, the free encyclopedia

Anything Into Oil | DiscoverMagazine.com

 

The solution.
Jatropha Curcas Plantations - About Jatropha Curcas

 

It's NOT impossible for the Mk7 Golf TDI (w/6spd) to attain 70-75 MPG (US) on the highway..... BUT I would say that hyper-miling is definitely necessary to reach those numbers. VW uses same 2.0L TDI motor used in the current Passat, which recently set the record at 77.99 MPG for a non-hybrid. This Guinness World Record was set in the USA. Without seeing all the specs, it's my *assumption* that the gear ratios on the Golf TDI are slanted more towards "fun" than "efficiency".

As for how long a VW diesel engine can last, especially when it's uses mostly as a highway hauler. Check out this thread on tdiclub. Look at the photo on post 133 (900,xxx miles).

 

Mk7 Golf TDI BlueMotion logged 80.5 MPG (converted to US gallon).

BlueMotion is a tweaked version of a regular Golf TDI (aerodynamic, regen braking, modded gearbox, LRR tires).

 

It's funny, we have heavy 2.0 TDI Passat with 140 HP, rated at 4.6 l/100 km on NEDC and a hypermiler can achive 77.99 MPG.

And then you have 1.6 TDI super eco friendly rated 3,2 l/100 km on NEDC only 105 HP Golf where a hypermiler aparantly only achives 80 MPG.

Is Wayne a god of hypermiling or is the new Golf bluemotion 30% better only on paper?

 

Hypermyling in a ICE-only engine means not urban cycle use...
NEDC is an average of urban/extraurban cycle.
And probably 2.0TDI has better BSFC value and sweet spot than 1.6

 

Go with the first. He did get over 100mpg out of a gen2 Prius.

It is also possible the Golf was being driven under a time limit.

 

I am a big VW fan (see my sig), but it really depends on the type of driving you do to see the benefits of the TDI over the Prius.

I honestly believe that a 1.6 or even a 2.0 TDI will be achieve better Mpgs with constant motorway driving at most speeds than a Prius, BUT, as soon as you hit amy city or town driving, the Prius will beat it hands down.

I generally rent TDIs a few times per year when holidaying in SPain and with almost all motorway driving it is better on fuel

 

I recently test drove the new Jetta Hybrid, not TDI, at the LA Auto Show. Impressed with the power & torque, didn't even drive like a hybrid. I'm guessing VW is looking to invest both un diesels & hybrids to remain competitive.

 

Considering the average mpg in the US 2013 is 23.6, any option is better. I have a 2010 Prius and a 2006 TDI Beetle (among other vehicles) and the only problem with the Beetle is/was the poor quality interior.

 

Psssssttt.........it's 2013.
Please, please, please, stop equating "hybrid" with "Prius".

Unless you fell asleep in 2003 and just woke up, I'm sure you are aware - I hope - that there are hybrids out there that can absolutely blow away your oil-burner. Still not convinced?

Can the VW beat this hybrid?
Ferrari’s new ‘mild hybrid’ LaFerrari supercar produces 963 hp | ExtremeTech
Or this hybrid?
Porsche’s new hybrid supercar: 918 Spyder - Slide Show - MarketWatch
How about this hybrid?
Everything you need to know about the Acura NSX hybrid supercar | Digital Trends
Do these cars "drive like a hybrid"? because, you know, they are.......
"drive like a hybrid"???? What the hell does that even mean? Who talks like that?

Oh, and I forgot this one:
McLaren P1: Million-dollar hybrid not driven by mpg - Chicago Tribune

 

Relax. Considering the price point of the VW Golf TDI, I think it is safe to assume jcal0820 statement "drive like a hybrid" was referring to less costly examples than yours.